Truss tile



1934. A. H. FARRENS 1,945,681

TRUSS TILE Filed July 9, 1931 2 Sheets-Sheet l 3 mw wroz A.]i] 'arrensA. H. FARRENS Feb. 6, 1934.

TRUSS TILE Filed July 9, 1931 2 Sheets-Sheet 2 3140mm A .HFar-rensPatented Feb. 6, 1934 .TRUSS TILE Albert II. Farrens, Lincoln, Nebr.Application July 9, 1931. Serial No. 549,715

1 Claim.

My invention relates to building tile and more particularly to the burntclay type of tile, the primary object of the invention being theprovision of a clay block having lighter weight and greater load bearingstrength than any of the tile heretofore known.

Another object of the invention is the provision of a tile having a formwhich will stand up under rough handling in the green state.

Another object of the invention is the provision of a tile having aplurality of substantially cylindrical cells surrounded by continuousrectangular walls which are tangential to the walls of the cylindricalcells and integral therewith.

Another object of the invention is the provision of a. tile designedwith reference to the lines of cleavage of the material from which thetile is made.

Another object of the invention is the provi-' sion of a tile made byforcing clay through a die, the die being so designed that the interiorfriction of the clay in passing through the die substantiallycounterbalances the exterior friction.

Another object of the invention is the provision of a tile having anexterior design so that the tile may be laid in the wall in any one ofthree positions and so that the mortar joint may be provided either withor without a dead air space.

Still another object of the invention is the pro sion of an end surfacefor the tile such as to provide ample keys for the mortar of the joints.

Having in view these objects and others which will be pointed out in thefollowing description, I will now refer to the drawings, in which IFigure 1 is a view in perspective of the truss tile.

Figure 2 is an end view of the tile showing particularly theappproximate positions of the lines of cleavage of the tile. The viewmight also be taken to represent a face view of the die used in formingthe block.

Figure 3 is a diagrammatic view of a portion of the end of the tileshowing particularly the truss formation of the tile upon which its loadbearing function depends.

The form of the block is shown in Figure 1. This block is rectangular inform and it is providedwith two large cells 10, the exterior walls ofthe block being rectangular and tangential and integral with the wallssurrounding the cells 10. Other but smaller cells 11 are provided ateach of the corners of the block. Along the median line between the twocells 10 are wedge-shaped cells 12 each having two walls which aresubstantially parallel to the webs between the side walls of the blockand the cells 10 are relatively wide and they areeach provided with oneor more small cells 13 in elliptical form.

Exteriorly the block is provided on each of two opposite sides with apair of semi-cylindrical channels 14. The space between the channels 14is grooved or corrugated at 15, and similar grooves or corrugations 16are provided in the spaces to the outer sides of the channels 14. In mydrawings I have shown one wall as left smooth at 17 while the oppositewall is provided with means for keying a plaster coat. If desired, bothopposite walls may be made smooth or with keyways for the plaster. Asshown in my drawings the plaster key is in the form of two corrugated orgrooved surfaces 18 with a smooth surface 19 between the corrugatedsurfaces 18. It is obvious, however, that the plaster keys may be in anydesired form and that the smooth walls may be omitted entirely if sodesired.

I shall now discuss the tile of this form with reference to itsmanufacture. Nearly all tiles at the present time are made by machinerywhich includes dies for giving the tiles the desired cross sectionalform. The thoroughly puddled clay is forced under powerful pressurethrough the die after which it is cut into the desired lengths. Thepressure is applied by means of an auger which gives the clay not only aforward movement but also a movement in a curvilinear direction aboutthe axis of the auger. The clay then leaves the die in the form of anendless column having .a longitudinal grain due to theforward impulseimparted, by the auger and having also avery decided curvilinear grain.T e grain in the clay is roughly in spiral form but closelyapproachingthe circular form. It is a well known fact that this grain is presentnot only in the green blocks but that it remains during burning and aslong as the block retains its form. The grain inthe block both in thegreen and in the burnt stages determines the lines of cleavage of theblock. The block in effect has a laminated structure.

The grain is further affected by various other factors. The clay in theauger is under powerful pressure and this pressure is greatest at theperiphery and least at the axis of the auger. This results in pronouncedlaminations at the outer edges of the block and with practically nograin whatever as the center of the block is approached; Then too, theauger has its forward end at some distance in the rear of the die. Asclay leaves the auger and a slight distance forward of the walls or thecells 10. The 5 i to better resist compression die, the clay has a voidin the space previously occupied by the shaft of the auger. Due tointernal pressure of the clay, this void becomes filled with clayresulting both in a slight change of direction of the weak grain andalso in a slight decrease in density of the clay at the center of theblock. The die is positioned in the machine with its center point inalignment with the projected axis of the auger so that the finishedblock as it leaves the auger will be symmetrical as regards the grain ofthe clay.

The machine manufacture of clay blocks involves still another problem.The clay has a more or less colloidal structure and when itis forcedunder powerful pressure through a die, the friction on the exteriorsurface of theblock will be so great as to cause a slightly more rapidmovement of the clay at the interior of the block. When the column isthen cut into blocks, the clay has a tendency to resume its normal formand in doing so the end portions will tend' to recede so that the endsof the block are apt to become concave. To avoid this it is necessarythat the die be so formed as to provide cells in the blocks, the purposebeing to introduce sufficient friction on the interior of the block tobalance the friction on the outer surface of the block. While the cellshave their primary function when the block is in use in the wall of abuilding, it is exceedingly important that they be so designed as tointroduce the proper amount of friction when the clay is passing throughthe die. Since the density of the clay at the center of the column isless than that at the outside of the column it is necessary that theoutlines of the cells be slightly greater than the exterior outline ofthe block.

The greatest resistance against distortion in any material is in thedirection of its grain. Referring now to Figure'Z of my drawings, thecircular lines represent approximately the directions of the grain inthe block. In the wall the block is subjected to forces producingcompression in the block. These forces are transmitted through the blockin the various webs surrounding the channels. The outer web 20 with thecells is so designed that the lines of cleavage are broken as little aspossible by the cells and so that these lines of cleavage will be in theapproximate position of the lines of force when the block is undercompression. I The direction of these lines of force is determined tosome extent by the truss formation of the block which will be discussedlater. At any rate it will be seen that the compression is transmittedthrough the strongest parts of the block and in the direction best ableto resist such forces. Under actual compression tests it has been foundthat the present block will withstand greater pressures than otherblocks which have been tested and that the present block will collapseentirely while the prior blocks show ruptures along the lines ofcleavage at a much lower pressure. The position of the cells withreference to the lines of cleavage not only enables the block after ithas been placed in a wall but this structure has important advantages innearly every step in its manufacture and use. The endless column leavingthe die is carried forwardly on a belt conveyor where it is first cutinto blocks of the desired length. The blocks are transported from theconveyor to carts usually in the hands of the workmen. The green blocksare handled rather roughly as they are subjected to frequent impacts intheir travel from the belt conveyor to the cart. Breakage is frequent inthe case of prior blocks because the position of the cells is usuallysuch as to shorten the lines of cleavage. The next step in themanufacture of the blocks is the drying which is then followed by theburning. The drying is performed as evenly as possible since unequaldrying results in strains and stresses which crack the block usuallyalong the lines of cleavage. Here again the function of the long linesof cleavage in the webs will be apparent. The greater length of theselines of cleavage will resist the tendency toward separation due touneven drying. The same is true when the blocks are in the kiln. Any

slight fluctuations in the heat to which the blocks are subjected areliable to cause unequal expansion and contraction but these forces alsoare resisted by the laminated structure of my block in which the linesof cleavage are relatively long.

The truss formation of the block can best be explained with reference toFigure 3. If the block were out along the vertical axes of the two cells10, the block would then be in the form of three pieces as shown inFigure 3. The middle of the three pieces is clearly in the form of anI-beam while the two end pieces are channel beams. The complete blockthus embodies a middle I-beam with two end channel beams all of integralstructure. The advantage of this construction in its load bearingproperties will be readily apparent to all those skilled in the art.

From the foregoing description it will be apparent that the abovedescribed block has nu-. merous advantages over the prior blocks. Thebreakage in handling and drying is reduced to a minimum because of thedesign whereby the cells are arranged with reference to the lines ofcleavage of the block. With the prior tiles the breakage in'handling anddrying usually runs from 5% to 25%. Under the same conditions ofhandling and drying the breakage of blocks of the above described typewill average from 1% to 3% thus effecting a great reduction in thebreakage of the tiles. This holds true in the subsequent handlingoperations of the tile which must first be introduced into the kiln forburning, then. removed from the kiln to a place of storage and thenhandled repeatedly during transportation before it reaches the ultimateuser. When ready to be placed in the wall it is again subjected to moreor less rough handling. At all places where the tile is handled, thebreakage is less than that of the prior tiles.

After the tile is in the wall whatever breakage there is, is due to itsstructural strength or weakness rather than to handling. It is at thisplace where the truss formation of my block proves the usefulness ofthat formation. The load carried by the block may crush the blockcompletely but it will not rupture the block as in thecase of the priorblocks. My block has, however, been subjected to crushing tests and ithas been found to greatly exceed in strength all requirements for blocksof this character.

The block also is provided with numerous cells of greater volume thanthose heretofore manufactured. This also is important at every step ofthe manufacture and use of the block. During every step of handling theblock is lighter in weight than the prior blocks thus enabling theworkmen to handle a larger number of the blocks to thus reduce the laborcost of handling. This reduction in weight is also of material benefitin the transportation of the tile since the freight tariffs are based onweight. The finished tile receives its final handling when it is placedby the mason in the wall. When it is in the wall the large number andvolume of the cells makes the block more elTective as an insulatoragainst heat and against moisture. The dead air spaces prevent thetransfer of heat through the Wall in both winter and summer and theythus make the building structure warmer in winter and cooler in summerthan the prior structures. The moisture also is more readily trapped inthe larger voids of my building tile so that practically no moisturewhatever can pass through the wall to dampen the interior of thestructure. The mouths of the relatively large number of cells alsoprovide ample keys for the mortar joints.

The exterior surface of my block has also been carefully designed forthe convenience of the mason and of the architect. The block may be madein any suitable dimensions and in any suitable size but the block asshown may be placed in a wall in any of three positions. When the weightof the wall above is great the block should be laid in the positionshown in Figure 2. The smooth face 1'7 may be provided as an exteriorface if it is desired to have a smooth unplastered face for the wall.The horizontal mortar joints may be applied either to the entire uppersurface of the block or to the surfaces 16 only. If applied to thesurfaces 16 and compression of the mortar will force some of the mortarinto the channels 14 to prevent the slippage of one block on the other,the blocks being in effect keyed to each other. The middle portion 15 ofthe block will then provide a dead air space to prevent the creeping ofmoisture through the mortar joint. If the mortar is placed over theentire upper surface of the block, the mortar will then be keyed notonly in the two channels 14 but also in the corrugated surfaces 15 and16. The ends of the block are buttered with mortar which keys readilyinto the numerous cells 10, 11, 12, and 13. If the block is to be placedin a vertical position in Figure l, the same advantages will outside, orone of the other walls may be positioned on the outside if it is desiredto give the exterior of the wall a plaster coat. In any case the blocksmay be secured together by means of mortar joints which readily becomekeyed to the blocks.

Having thus described my invention in such full, clear, and exact termsthat its construction and operation will be readily understood by othersskilled in the art to which it pertains, what I claim as new and desireto secure by Letters Patent of the United States is:

A building block comprising a body portion having a pair of spaced apartcells and an intermediate web having a height substantially equal tohalf the thickness of the block, each end of said web terminating in aT-head, each T-head having a relatively small air opening therebyproviding a pair of short, thick arcuate bracing arms, the outer ends ofwhich merge into the respective ends of the T-head and the outer surfaceof the block and the inner ends of which merge into the web, said bodyportion also having at each outer portion a Web having a heightsubstantially equal to that of the first mentioned web and terminatingat each end in an angle head which extends inwardly toward the T-head,each angle head having a relatively small air opening to provide ashort, thick arcuate bracing arm, the outer end of which merges into theangle head and outer surface of the block and the inner end of whichmerges into the second mentioned web.

ALBERT H. FARRENS.

